A rate "lock" or "commitment" is a lender's promise to lock in a specific interest rate and a specific number of points for you for a specified period of time during your application process. This prevents you from getting through your whole application process and finding out at the end that the interest rate has gotten higher.
While there can be a choice of rate lock periods (from 15 to 60 days), the extended spans are usually more expensive. You can get a longer period for your lock, but in choosing this option, will probably have a higher rate than you would with a shorter rate lock period
There are other ways to get a good rate, in addition to choosing a shorter rate lock period. The bigger down payment you can make, the better your interest rate will be, since you will have more equity from the beginning. You could choose to pay points to improve your rate for the loan term, meaning you pay more up front. One strategy that makes financial sense for some is to pay points to bring the rate down over the life of the loan. You will pay more up front, but you will come out ahead in the long run.
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